Telepresence competitions can be designed
around a scientific remotely-controlled robot
exploring a cave, underwater location, the moon,
or even Mars. Control delays can be built in to
simulate the moon’s three second delay or Mars’
delay of several minutes. Scoring can be based on
speed, retrieval of ‘moon rocks,’ location of water
— all done by remote control from a location
hidden from the competitor’s view.

Observers can watch the actual rovers
operate. Both R/C and autonomous functions can
be used, and the more sensors used, the easier
the task. Just as Robo-Magellan was based on the
DARPA Grand Challenge, scaled-down robotic
competitions can mimic present-day scientific uses
and allow home experimenters to build smaller

Basic home-built robot designs have changed
very little over the past three decades. Virtually all
experimenter’s wheeled robots employ differential
steering. The reason for this is simple: If you apply
the same power to each wheel and count the
wheel turns by an encoder or use a stepper motor,
the robot will go straight. Opposite polarity to the
wheels will cause the robot to rotate on its axis,
and variations will allow the robot to turn. This
works fine if there is no wheel slippage.

The Ackermann design is a bit more complex
for beginners as it requires building interconnected
steering mechanisms for the front (or back)
wheels, and the programming requires input to a
steering motor and to the main wheel drive
motor(s). If designed correctly, the resulting
steering can be much more accurate than
differential steering but a lot of builders find the
programming a bit beyond their capabilities.
Several robots are now using off-road R/C car
bases with Ackermann steering, and adding a
microcontroller and sensor suite to build a great
robot.

Experimenter-level robots used switches as
feelers for years, but now have started using
IR/visible light beams to detect obstacles and
walls. Maxsonar, Devantech, and Parallax make
nice and inexpensive ultrasonic sensors to detect
objects. However, the old Polaroid electrostatic
sonars with their narrow beam are still a favorite
with many builders. The (far) more expensive but
vastly superior laser range finders made by Sick,
Hokuyo, and other high end suppliers are finding
their way onto a few more sophisticated robots.
The selection of sensors of the above might be
dependent upon what type of background the
robot is operating with, such as grass, carpet, or a
hard floor. Balancing robots utilize accelerometers
and gyros for sensors. You can get a combination
of both with SparkFun’s 6DOF Razor that has
gyros and accelerometers in all three axes,
available on a small printed circuit board.

Intelligent cameras such as the CMU camera
can be indispensible as a main sensor for more
complex robot designs. Many people are looking
to go beyond a simple differential wheel robot
that can follow a maze and develop a robot that
can operate in the cluttered environment of a
home. Dave Shinsel is shown in Figure 7
demonstrating Loki to SRS’s Cathy Saxton at the
2009 Robothon. Using simple web cams and
deriving visual intelligence through the use of an